Popular wisdom has it that you stop noticing differences after a while.
Actuality begs to differ.
You can’t do assignments with classmates in your free time, for example, without taking religion into account.
Say you have something due on Monday. It is now Friday.
You can’t do it by lunch today if your partner is a religious Muslim.
If you partner with a non-Orthodox Jew, you have to somehow try to ensure he doesn’t work on it on Saturday.
It is not a good idea to do the assignment with a religious Mormon at all, because you are unavailable on Saturday and she is unavailable on Sunday.
If you stop noticing religion much, you can end up doing your assignment in a rushed hour or two the morning it’s due. Not fun.